1. Field of the Invention
The present invention relates to an electromagnetic stirring device (1) of melted metallic material inside a cooling chamber (30) of a casting machine (18) according to the characteristics of the pre-characterizing part of claim 1.
This invention relates also to a casting machine (18) according to the characteristics of the pre-characterizing part of claim 17.
The present invention also relates to a casting process for the production of metallic material bars (16) according to the characteristics of the pre-characterizing part of claim 20.
Definitions
Herein description and in the appended claims the following terms must be intended according to the definitions given in the following.
With the expression “metallic bar” it is intended to include all types of products of a casting machine, e.g. billets, blooms or flat blooms with different shapes in section e.g. with square, rectangular, round, polygonal section.
With the expression “casting machine” it is intended to include both vertical casting machines and casting machines provided with bending.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
In the field of the execution of continuous casting plants of metallic materials, in general steels and metallic alloys, the recourse to electromagnetic stirring devices of the melted metallic material generally known with the name of stirrers, is known.
The stirrer produces a magnetic field generating a force inside the die or mould within which there is the melted metallic material inducing a rotating flow inside the melted bath obtaining a stirring effect of the same. In the die or mould occurs the cooling of the surface or skin of the metal bar that is generated in the die itself and, in correspondence with the outlet of the metal bar from the die or mould, it presents a solidified perimetrical zone or shell having a 10-30 mm thickness inside which there is a nucleus in which the metallic material is still at the melted state and that is progressively solidified when the metallic bar advances within a cooling chamber of the casting machine in which it is subject to the action of cooling groups that in general consist of sets of water sprayers. Applications of the stirrers both in correspondence with the die or mould within which the introduction of the melted metallic material occurs and applications of the stirrer at the cooling chamber of the casting machine to obtain qualitative improvements of the metallic bar structure to reduce the occurrence of deficiencies during the solidifying phase are known. The stirrer consists of a housing inside which some electrical windings are placed for the passage of the current that induces the electromagnetic stirring field and the housing presents an open duct within which the incandescent metallic bar in the formation process passes. For example the recourse to the stirrers contributes to reduce inclusions and surface and subcutaneous blowholes, cracks, porosity, segregation and contributes to improve the solidifying structures.
The prior art stirrers are usually mounted in fixed position determined on the basis of the characteristics of the casting machine and of the process according to a solution of compromise between the optimal different positions that would be required according to the process variations and to the sections of the cast metallic bars.
The Patent Application EP 2127783 A1 describes an electromagnetic stirrer that is intended to be installed around the steel discharger from the tundish to the mould of a continuous casting machine, in which the electromagnetic stirrer including a nucleus composed of two different circumferential portions around which a plurality of windings is wound.
The Patent Application US 2008/164004 A1 describes an electromagnetic stirrer that is intended to be installed along different billet portions in the process of production in a continuous casting machine.